Airplane strut



Oct. 11, 1932. F WALLACE 1,882,349

AIRPLANE STRUT Filed May 10l 1930 illlllllllllllll .20 21 ai 2 'f/ l Y la 2,

l 75, GLZZJ.

. Pauneedea'll, 1932 UNITED STATES` PATIENT- OFFICE JOBI l'. WALLACE, Ol' am, OHIO, ASSIGNOB TO m m130 TOOL conm, OIACLIVMD, OHIO, .l CORPORATION Ol' OHIO mm3 BTBUT Applicatie! lied Il! 10, 1m. .trial le. 451.

This invention relates to improvements in airplane struts, more particularly hydfropneumatic shock absorbers for airplanes and other vehicles.

One of the objects of the invention 1s the provision of a strut of this character having a valve construction of extreme simplicity.

Another object is the rovision of a strut which may be uickly an easily disassembled and reassemb ed for servicing and repa purposes.

Another obect is the provision of a construction in which the valve seat and the packin piece t at is removably attached to the 'end of the inner cylinder.

Other objects and features of novelty wlll, appear as I proceed with the descriptlon of that embodiment of the invention which, for the purposes of the present application, I have illustrated in the accompanying drawiniz in which igure 1 is an elevational view of one embodiment of the invention, certain parts being broken away and others shown in vertical central section in order to more fully illustrate the invention.

Figure 2 is a cross sectional detail view taken substantially on the line 2-2 of Figure 1.

In the drawing I have shown two cylinders 10 and 11 constructed of sheet metal tubing, steel tubing being the preferred material. At their outer ends these cylinders are spun inwardly to form cylinder heads 12 and 13 respectively. Onto these heads there may be welded tubular pieces 14 and 15, to which the fittings for attachment to the wings or fuselage of the air lane and its running gear may be secure In the upper end o cylinder 10 I provide a filler openin 16.for the -oil and an air valve 17 throug which the strut may be inflated. Near the bottom of cylinder 11 I mount a metal-reinforcing disk 18. This 'disk may be welded tothe interior wall of the cylinder before the metal is spun over beneath it. Cylinder 11 is internally threaded at its upper end -for the reception of a sto Aring size to till the holder are. contained vin a. singlev space between the two cylinders and slida ly fit the cylinder 10. This ring is serrated or otherwise formed for ready manipulation, so that it may be easily applied and removed when n f ry. The 'ring 19 serves, of course, as a reinforcement, as well as a means for limiting the extension of the strut and guiding the cylinder 10. v The outer end of the cylinder 10 is threaded for the rece tion of a shank portion 20 of a piston heacl) structure. shank -portion is of the same thickness as tllie stop ringA 19, so as totill the space between Vthe cyhnders and guide the movement of the cylinder 10. As shown in the drawing, the u shank portion 20 extends for a distance beyond t e' end of the cylinder 10, where it merges into an inwardly 'extending annular shoulder 21 which joints the portion 20 with an offset c lindrical portion 22, formin the inner wal of an annular recess 23. acking of any suitable character is mounted in the recess 23. In the present instance this packing takes the form of two resilient packing rings 24 and 25 separated by a metallic spacing ring 26. The rin 24, 25 and 26 may be held against acci ental movement downward relative to the piston head b a metal ring 27 which is threaded tothe cy indrical portion 22 thereof. n

The corner of the piston head structure at the juncture of the shoulder 21 and the cylindrical portion 22 is machined oi to form a conical vvalve seat 28. A disk shaped valve piece 29, having' a complementary lsurface, u 1s adapted to rest upon this seat normally. It is provided with a continuously vopen ort 30, the size of which may be varied as desired to control the speed of the reboundl action of the strut. Tolimit the upward movement of the valve seat and to guide its vertical movement, I provide the valve piece with three extensions 31 loosely engaging the inner wall t of the shank portion 20 of the piston head structure, and adapted to engage the end surface of the cvlinder 10 when the' valve opens. e Y

In order to put the strut into service, its ends are attached by suitable means be- `tween the parts of an airplane whose rela 100 tive movements are to be cushioned, it being lllnderstood that this arrangement shall bring the strut into an approximately upright position. Oil is then poured ,into the strut through the filler opening 16 to substantially fill the strut in its compressed condition. This opening is then closed, and a compressed air line is attached to the air valve 17, and the strut is inflated to a predetermined extent. that is suliiciently to extend the cylinders 10 and 11 the required amount. In

Fig. 1 they are illustrated as extended to the limit, which condition will obtain only when the plane is in flight. When the plane alights upon the ground, the running gear is forced upward suddenly and delivers a heavy impact in the upward direction to the cylinder 11, causing the two cyllnders l and 11 to telescope together. The oil 1n cylinder 11 therefore seeks to ilow into c linder 10. Being unable to flow with suflicient rapidity through port 30, it raises the valve piece 29 and flows through the annular opening surrounding the valve plece. Now, when the air in cylinder has been compressed to the extent where its pressure equals the pressure of the impact, the tele scoping movement stops, and the highly .compressed air in cylinder 10 tends to again expand the cylinders rapidly. In the present construction this rebound movement is checked; because the valve piece 29 immediately seats itself upon the seat 28, whereupon all further transfer of oil from the cylinder 10 to the cylinder 11 must take place through the port 30. The rebound stroke is therefore slowed up accordingly.

Whenever it becomes necessary, for any reason, to remove the valve piece 29, the stop ring 19 is merely unscrewed, the cyllnder 11 is pulled outwardly over the piston head, and then the latter is unscrewed from the cylinder 10. The removal of the cylinder 11 also, of course, exposes the packing rings 24, 25,

26 and 27, and these rings may be repaired or replaced without the removal of the piston head from the cylinder 10. However, if a very quick repair is needed, the entire piston head structure may be unscrewed from the cylinder 10 and a new one together with a new valve piece 29, may be put in place, after which any necessary repairs to the removed unit may be efected whenever it becomes convenient to do so. Y

While in the foregoing description and in the accompanying drawing I have disclosed 'one particular embodiment of the invention more or less in detail` I desire it to be under-y stood that such detailed disclosure has been resorted to primarily for the purpose' of fully illustrating the invention in conformity with the requirements of the statute, and thatv it is not to be construed as amounting to a limitation upon the scope of the invention.

Having thus described my invention, I claim l 1. In a fluid strut, a pair of telescoping cylinders, a piston head structure threaded upon the inner end of the inner cylinder and protruding therebeyond, said structure having an inturned portion spaced from the end of the inner cylinder, an inwardly facing valve seat on said inturned portion, and a valve piece adapted to co-operate with said seat, theinner end of the inner cylinder constituting means for limiting the opening movement of the valve piece.

2. In a fluid strut, a pair of telescoping cylinders, a piston head structure threaded upon the inner end of the inner cylinder and protruding therebeyond, said structure havy ing an inturned ortion spaced from the end of the inner cy inder, an inwardly facing valve seat on said inturned portion, and a valve piece adapted to co-operate with said seat, the inner end of the inner cylinder constituting means for limiting the opening movement of the valve piece, said head structure beyond said valve carrying annular packing adapted to engage the outer cylinder.

3. In a fluid strut, a pair of telescoping cylinders with spaced walls, the inner cylinder being externally threaded at its inner end, `a piston head structure threaded thereupon protrudin beyond the end thereof, said head structure aving an inturned portion spaced from the end of the inner cylinder, a

valve seat' on said inturned portion, and a disk shaped valve piece adapted to cooperate with said seat, and having extensions for engagement with the side walls of said head structure and with the end of said inner cylinder to center the valve piece and to stop the opening movement of the yalve.

4. In a fluid strut, a pair of telescoping cylinders with spaced walls, a piston head structure secured upon the inner end of the inner cylinder and protruding there beyond, said head structure having a valve seat facing the end of said inner cylinder, and spaced from the end thereof, said head structure having an annular external recess beyond said valve seat, packing means in said recess contacting with the outer cylinder, and a valve piece mounted between said valve seat and the inner end of said inner cylinder.

5. In a fluid strut, a pair of telescoping c linders, the inner end of the smaller cylin er beingexternally threaded, a head structure comprising a largediameter portion and a small diameter portion connected by a transverse annular portion, said large diameter portion being threaded onto the threaded end of said smaller cylinder, said annular portion forming a valve seat, a valve for said seat, and said small diameter ortion carrying an external packing adapted, to engage the wall of the larger cylinder.

6. In a uid strut, a pair of tubular sheet signature.

\ JOHN F. WALLACE. 

